# Single-photon computational 3D imaging at 45 km

## TL;DR

This paper demonstrates a novel single-photon LiDAR system capable of high-resolution 3D imaging at distances up to 45 km in urban environments, overcoming noise challenges with advanced algorithms and system design.

## Contribution

The authors developed a high-efficiency, low-noise confocal single-photon LiDAR system and a tailored computational algorithm enabling super-resolution 3D imaging over unprecedented long distances.

## Key findings

- Successfully imaged at 45 km with ~1 photon per pixel
- Achieved high photon efficiency and super-resolution
- System feasibility for hundreds of kilometers with further refinement

## Abstract

Long-range active imaging has a variety of applications in remote sensing and target recognition. Single-photon LiDAR (light detection and ranging) offers single-photon sensitivity and picosecond timing resolution, which is desirable for high-precision three-dimensional (3D) imaging over long distances. Despite important progress, further extending the imaging range presents enormous challenges because only weak echo photons return and are mixed with strong noise. Herein, we tackled these challenges by constructing a high-efficiency, low-noise confocal single-photon LiDAR system, and developing a long-range-tailored computational algorithm that provides high photon efficiency and super-resolution in the transverse domain. Using this technique, we experimentally demonstrated active single-photon 3D-imaging at a distance of up to 45 km in an urban environment, with a low return-signal level of $\sim$1 photon per pixel. Our system is feasible for imaging at a few hundreds of kilometers by refining the setup, and thus represents a significant milestone towards rapid, low-power, and high-resolution LiDAR over extra-long ranges.